1. Field of the Invention
The present invention relates to a sheet separator, and particularly to a sheet separator with adjustable feed angle.
2. Description of the Related Art
The application of business machines in offices like printers, fax and copy machines have become more and more popular. Regarding business machines processing paper, media-feed mechanism has a great influence on efficiency. Therefore, it has become a new challenge to design a highly efficient media-feed mechanism to feed and separate media readily.
In general, with printers as an example, an automatic media-feed mechanism is utilized to feed the media. Before printing, users normally put the media in the media-feed mechanism. To print, media are moved out one by one through the media-feed mechanism.
Referring to FIG. 1A, an automatic media-feed mechanism has a bottom surface 101 to carry the media. The roller 150 is above the bottom surface 101 to drive the media. In particular, a sheet separator 103 and several smooth ribs 102 are disposed on the bottom surface 101. When the media are driven by the roller 105, the sheet separator 103 separates the media one by one and the ribs 102 keep the individual media moving out smoothly.
In FIG. 1B, a sheet separator 103 and several ribs 102 disposed on the bottom surface 101 of the automatic media-feed mechanism are parallel to the moving direction of the media. The ribs 102 sustain and keep the individual media sliding smoothly. In practice, the ribs 102 are plastic or metal with a smooth surface and have a low friction coefficient. Referring to FIG. 1C, the medium is driven by the roller 150 (not shown) in the direction A. The leading edge 107 of the medium 105 contacts the ribs 102 when moving.
As shown in FIG. 1D, when the medium 105 moved in direction A, the leading edge 107 of the medium 105 contacts the ribs 102 and the sheet separator 103. At the same time, the ribs 102 and the sheet separator 103 exert a frictional force on the medium 105 in direction B opposite to the direction A. In particular, the frictional force increases with the stiffness of the medium 105. Thus, the driving motor may be overloaded, missing steps, and the leading edge 107 of the medium 105 may be damaged by using excessively stiff media.
It is known that there are many categories of media made of different material of varying thickness (g/m2). Therefore, as shown in FIG. 1E, the sheet separating angle α is determined according to the corresponding available medium thickness. Only the media within a particular range of thickness are available when the sheet separating angle α is determined. For example, the sheet separator 103 may allow only media within stiffness of 70 g/m2 to 80 g/m2, but not for media with stiffness out of this range.
For this reason, the conventional sheet separator may cause multiple media feed at the same time and make the driving motor lose step by using excessively stiff media. Thus, the conventional sheet separator is only suitable for media in a particular range of thickness but cannot be widely used.